Hybrid vehicle controller

ABSTRACT

A power frequency distribution predicting unit predicts the power frequency distribution of a vehicle in a case where the vehicle travels a route with reference to the history of the vehicle power Pv when the vehicle traveled the route in the past. An operation condition setting unit sets the range of the required vehicle power Pv 0  to operate the engine as an engine operation condition for controlling the energy balance between generated power and generated electric power of an electric rotating machine in a case where the vehicle travels the route to be at a preset value according to the power frequency distribution predicted by the power frequency distribution predicting unit. An operation control unit controls the operation of the engine according to the range of the required vehicle power Pv 0  to operate the engine set by the operation condition setting unit.

This is a Division of application Ser. No. 12/223,824 filed Aug. 11,2008, which claims the benefit of JP 2006-043750 filed Feb. 21, 2006 andPCT/JP2007/053695 filed Feb. 21, 2007. The disclosure of the priorapplications is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a hybrid vehicle controller, and moreparticularly, to a controller used in a hybrid vehicle capable ofdriving the drive wheels using power generated by at least one of theengine and the electric rotating machine and generating electric powerby means of the electric rotating machine using power generated by theengine.

BACKGROUND ART

A related art of a hybrid vehicle controller of this type is disclosedin JP 3654048 B (hereinafter, referred to as Patent Document 1). Thehybrid vehicle controller according to Patent Document 1 includes: pathsearching means for searching a path to the destination; road conditiondetecting means for detecting the road condition of the path; pathdividing means for dividing the path into plural zones at points wherestarting and stopping are predicted; driving history recording means forrecording therein a driving history of the driver; vehicle speedestimating means for estimating a vehicle speed pattern for each zonewith reference to the road condition and the driving history; andoperation schedule setting means for setting operation schedules for theengine and the motor for each zone according to the vehicle speedpattern and the fuel consumption characteristic of the engine so as tominimize a fuel consumption amount to the destination. The operationschedule setting means compares a fuel consumption amount resulting froma first operation schedule, according to which the vehicle travels byoperating the motor in a zone where the operation efficiency of theengine becomes low (hereinafter, referred to as the low efficiency zone)while the battery is charged by driving the motor to generate electricpower using a power, which is a difference when a power need for thetravel is subtracted from a power of the engine, by making the power ofthe engine larger than the output needed for the travel by shifting theoperation point of the engine in the other zones such that the operationefficiency is increased, with a fuel consumption amount resulting from asecond operation schedule, according to which the vehicle travels byoperating the engine alone in the low efficiency zone and the otherzones, and chooses the first operation schedule in a case where the fuelconsumption amount resulting from the first operation schedule issmaller than the fuel consumption amount resulting from the secondschedule. Accordingly, the operation schedules for the engine and themotor are set so as to minimize the fuel consumption amount of theengine in response to the road condition of the route to thedestination.

According to Patent Document 1, in a case where the first operationschedule is chosen, whether the vehicle travels by operating the motoror by operating the engine is set for each of the zones divided atpoints at which starting and stopping are predicted. However, in a casewhere a region where the vehicle requirement power is low and a regionwhere the vehicle requirement power is high are present together in thesame zone, it becomes difficult to set the operation schedules for theengine and the motor appropriately. For example, either the vehicletravels using a power of the engine even in a region in which theoperation efficiency of the engine is low, or the vehicle travels usinga power of the motor even in a region in which the operation efficiencyof the engine is high. Also, according to the method for setting whetherthe vehicle travels by operating the motor or by operating the engine ona zone by zone basis for the path divided into plural zones, the settingmade in one zone affects the other zones. Accordingly, either a massivevolume of computation is required to set the operation schedules for theengine and the motor appropriately for the entire route, or it becomesimpossible to achieve the most appropriate operation schedules for theengine and the motor for the entire route.

DISCLOSURE OF THE INVENTION

The invention provides a hybrid vehicle controller capable ofcontrolling the operation of the engine more appropriately.

A hybrid vehicle controller of the invention is a controller used in ahybrid vehicle capable of driving drive wheels using power generated byat least one of an engine and an electric rotating machine, and capableof generating electric power of the electric rotating machine using thepower generated by the engine, and characterized by including: anoperation control unit that controls operations of the engine and theelectric rotating machine according to required vehicle power; a powerfrequency distribution predicting unit that predicts a power frequencydistribution of the vehicle in a case where the vehicle travels a route;and an operation condition setting unit that sets an engine operationcondition to control an energy balance between generated power andgenerated electric power of the electric rotating machine in a casewhere the vehicle travels the route so as to fall within a preset rangeaccording to the power frequency distribution predicted by the powerfrequency distribution predicting unit, wherein the operation controlunit controls an operation of the engine according to the engineoperation condition set by the operation condition setting unit.

Also, another hybrid vehicle controller of the invention is a controllerused in a hybrid vehicle capable of driving drive wheels using powergenerated by at least one of an engine and an electric rotating machineand capable of generating electric power of the electric rotatingmachine using the power generated by the engine, and is characterized inthat the electric rotating machine is capable of sending electric powerto, and receiving the electric power from, an electric energy storagedevice that stores electric energy, and that the hybrid vehiclecontroller includes: an operation control unit that controls operationsof the engine and the electric rotating machine according to requiredvehicle power; a power frequency distribution predicting unit thatpredicts a power frequency distribution of the vehicle in a case wherethe vehicle travels a route; an electric energy storage state acquiringunit that acquires an electric energy storage state of the electricenergy storage device; and an operation condition setting unit that setsan engine operation condition for the electric energy storage state ofthe electric energy storage device after the vehicle has traveled theroute so as to fall within a preset range according to the powerfrequency distribution predicted by the power frequency distributionpredicting unit and the electric energy storage state of the electricenergy storage device acquired by the electric energy storage stateacquiring unit, wherein the operation condition unit controls anoperation of the engine according to the engine operation condition setby the operation condition setting unit.

According to the invention, by predicting the power frequencydistribution of the vehicle in a case where the vehicle travels theroute and controlling the operation of the engine for the energy balancebetween generated power and generated electric power of the electricrotating machine in a case where the vehicle travels the route so as tofall within the preset range according to the predicted power frequencydistribution, it is possible to control the operation of the engine moreappropriately.

Also, according to the invention, by predicting the power frequencydistribution of the vehicle in a case where the vehicle travels theroute and controlling the operation of the engine for the electricenergy storage state of the electric energy storage device after thevehicle has traveled the route so as to fall within the preset rangeaccording to the predicted power frequency distribution, it is possibleto control of the operation of the engine more appropriately.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is view schematically showing the configuration of a hybridvehicle including a controller according to one embodiment of theinvention.

FIG. 2 is a view showing an example of the configuration of anelectronic control unit.

FIG. 3 is a view used to describe an optimal fuel consumption line of anengine.

FIG. 4 is a view showing one example of a power frequency distributionof a vehicle.

FIG. 5 is a flowchart detailing an operation in a case where the vehicletravels from a departure place to a destination.

FIG. 6 is a flowchart detailing processing to set a lower limit value ofa range of required vehicle power to operate the engine.

FIG. 7 is a view used to describe processing to set the lower limitvalue of the range of the required vehicle power to operate the engineusing a power frequency distribution.

FIG. 8 is a view showing an example of the characteristic of a fuelconsumption rate with respect to power of the engine in a case where therotational speed and the torque of the engine are positioned on theoptimal fuel consumption line.

FIG. 9 is a view used to describe processing to set electricitygenerating power of a generator used to charge a rechargeable battery.

FIG. 10 is another view used to describe processing to set electricitygenerating power of the generator used to charge the rechargeablebattery.

FIG. 11 is a view showing one example of the characteristic of a fuelconsumption amount with respect to power of the engine.

FIG. 12 is a flowchart detailing another operation in a case where thevehicle travels from a departure point to a destination.

FIG. 13 is a flowchart detailing processing to correct the lower limitvalue of the range of the required vehicle power to operate the engine.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of the invention will be describedin accordance with the drawings. FIG. 1 is a view schematically showingthe configuration of a hybrid vehicle including a controller accordingto one embodiment of the invention. An output shaft of an engine(internal combustion) 50 capable of generating power is coupled to apower distribution mechanism 52. Besides the output shaft of the engine50, an input shaft of a speed reducer 14 and a rotator of a generator(power generating machine) 54 capable of generating electric power arealso coupled to the power distribution mechanism 52. The powerdistribution mechanism 52 referred to herein can be formed, for example,of a planetary gear mechanism having a ring gear, a carrier, and a sungear. The output shaft of the speed reducer 14 is coupled to the drivewheels 19. The power distribution mechanism 52 distributes power fromthe engine 50 to the drive wheels 19 and the generator 54. The powerdistributed to the drive wheels 19 from the power distribution mechanism52 is used to drive the vehicle. Meanwhile, the power distributed to thegenerator 54 from the power distribution mechanism 52 is converted togenerated electric power of the generator 54. It is possible to supplythe generated electric power of the generator 54 to a motor 10 capableof generating power via an inverter 12 (power converter). It is alsopossible to accumulate the generated electric power of the generator 54in a rechargeable battery 16 via the inverter 12. Further, it ispossible to start the engine 50 by generating power by the generator 54.

Electric power from the rechargeable battery 16 provided as an electricenergy storage device to store electric energy therein is supplied tothe winding wire of the motor 10 after it is subjected to powerconversion (converted from direct current to alternating current) by theinverter 12. The motor 10 converts the electric power supplied to thewinding wire via the inverter 12 to power of the rotator. The rotator ofthe motor 10 is coupled to the input shaft of the speed reducer 14, andthe power of the motor 10 is transmitted to the drive wheels 19 afterthe speed is reduced by the speed reducer 14 and used to drive thevehicle. In addition, the power of the drive wheels 19 (the vehicle) maybe converted to generated electric power of the motor 10 by aregenerative operation of the motor 10 so as to be accumulated in therechargeable battery 16 via the inverter 12. As has been described, thehybrid vehicle of this embodiment is provided with the motor 10 capableof driving the drive wheels 19 and the generator 54 capable ofgenerating electric power using power generated by the engine 50 as anelectric rotating machine. The electric rotating machine (the motor 10and the generator 54) is capable of receiving electric power from, andsending electric power to, the rechargeable battery 16. It is possibleto drive the drive wheels 19 (the vehicle) using power generated by atleast one of the engine 50 and the electric rotating machine (the motor10). Further, it is possible to generate electric power by means of theelectric rotating machine (the generator 54) using the power generatedby the engine 50.

A vehicle position detector 32 detects the current position of thevehicle using, for example, the GPS, and outputs a signal specifying thecurrent position of the vehicle to a navigation system 36 and anelectronic control unit 42. The navigation system 36 pre-stores road mapdata in a map database. It reads out the road map in the vicinity of thecurrent position of the vehicle from the map database and displays thisroad map on the screen together with the current position of thevehicle. In a case where an operator inputs the destination of thevehicle, the navigation system 36 sets a route of the vehicle accordingto the current position of the vehicle (departure place) and thedestination of the vehicle and displays the route on the screen. Thenavigation system 36 outputs a signal indicating the route of thevehicle to the electronic control unit 42.

The electronic control unit 42 is formed as a micro processor having aCPU that plays a central role, and includes a ROM that has pre-storedtherein a processing program, a RAM that temporarily stores thereindata, and input and output ports. Signals, such as a signal indicating avehicle speed V detected, a signal indicating an accelerator opening A,a signal indicating a brake operation amount B, a signal indicating arotational speed Ne of the engine 50, a signal indicating a rotationalspeed Nm of the motor 10, a signal indicating a rotational speed Ng ofthe generator 54, a signal indicating a current Im of the motor 10, asignal indicating the current Ig of the generator 54, a signalindicating the current Ib of the rechargeable battery 16, and a signalindicating a voltage Vb of the rechargeable battery 16 by anunillustrated sensor, are inputted into the electronic control unit 42via the input port. Further, signals, such as a signal specifying thecurrent position of the vehicle from the vehicle position detector 32and a signal indicating the route of the vehicle from the navigationsystem 36, are also inputted to the electronic control unit 42 via theinput port. Meanwhile, signals, such as an engine control signal tocontrol the operation of the engine 50, a motor control signal tocontrol the operation of the motor 10, and a generator control signal tocontrol the operation of the generator 54, are outputted from theelectronic control unit 42 via the output port.

The electronic control unit 42 can be formed, for example, by thefunctional block diagram as is shown in FIG. 2. The electronic controlunit 42 includes an operation control unit 60, a route predicting unit62, a power acquiring unit 64, a power frequency distribution storageunit 66, a power frequency distribution predicting unit 68, an electricenergy storage state acquiring unit 70, and an operation conditionsetting unit 72, all of which will be described below.

The operation control unit 60 sets required vehicle power Pv0 according,for example, to the accelerator opening A, the brake operation amount B,and the vehicle speed V. The operation control unit 60 controlsoperations of the engine 50 and the electric rotating machine (the motor10 and the generator 54) according to the required vehicle power Pv0.The operations of the motor 10 and the generator 54 can be controlled bycontrolling the switching operations of a switching element of theinverter 12. Also, the operation of the engine 50 while the engine 50 isgenerating power is controlled in such a manner so as to maintain astate where the rotational speed Ne and torque Te of the engine 50 arepositioned, for example, on (or almost on) an optimal fuel consumptionline shown in FIG. 3 (a line linking points at which the efficiencybecomes the highest for the engine power supplied).

The route predicting unit 62 predicts a route of the vehicle. Herein, itis possible to predict a route in a case where the vehicle travels theroute from the departure point to the destination from the route set bythe navigation system 36.

The power acquiring unit 64 acquires vehicle power (travel power) Pv ina case where the vehicle travels the route from the departure point tothe destination. Herein, the power Pv of the vehicle (the drive wheels19) can be estimated, for example, from the required vehicle power Pv0set by the operation control unit 60. It is also possible to detect thepower Pv of the vehicle (the drive wheels 19) according to therotational speed Ne and the torque Te of the engine 50, the rotationalspeed Nm and the torque Tm of the motor 10, and the rotational speed Ngand the torque Tg of the generator 54. The torque Te of the engine 50can be estimated according, for example, to a throttle opening C and theengine rotational speed Ne detected by an unillustrated sensor. Thetorque Tm of the motor 10 and the torque Tg of the generator 54 can beestimated, respectively, for example, from the current Im of the motor10 and the current Ig of the generator 54 detected by unillustratedcorresponding sensors.

The power frequency distribution storage unit 66 stores (accumulates) apower frequency distribution of the vehicle (the vehicle power(traveling power) and the frequency of use (time) thereof). The powerfrequency distribution of the vehicle referred to herein can beexpressed, for example, as is shown in FIG. 4, by times (frequencies)tb(i) included in respective power bandwidths (traveling powerbandwidths) Pb(i) (i is a natural number), which are the vehicle powerPv acquired by the power acquiring unit 64 that is divided into pluralbandwidths in advance. The power frequency distribution storage unit 66stores the value of tb(i) for each power bandwidth Pb(i). The powerfrequency distribution storage unit 66 stores the power frequencydistribution (the value of the frequency tb(i) in each power bandwidthPb(i)) in correlation with the route of the vehicle. Further, the powerfrequency distribution stored in the power frequency distributionstorage unit 66 is updated according to the vehicle power Pv acquired bythe power acquiring unit 64. To be more concrete, in the power frequencydistribution corresponding to the route of the vehicle predicted by theroute predicting unit 62, the value of the frequency tb(i) correspondingto the power bandwidth Pb(i) including the vehicle power Pv is updatedwhile the vehicle is traveling. As has been described, the powerfrequency distribution of the vehicle with reference to the history ofthe vehicle power Pv acquired by the power acquiring unit 64 is stored(accumulated) in the power frequency distribution storage unit 66.

The power frequency distribution predicting unit 68 predicts the powerfrequency distribution of the vehicle in a case where the vehicletravels the route from the departure place to the destination. Herein,the power frequency distribution (the value of the frequency tb(i) ineach power bandwidth Pb(i)) corresponding to the route of the vehiclepredicted by the route predicting unit 62 is read out from the powerfrequency distribution storage unit 66, and the power frequencydistribution thus read out is used as the predicted power frequencydistribution. In other words, in a case where the vehicle travels theroute from the departure point to the destination, the power frequencydistribution predicting unit 68 predicts the power frequencydistribution (the value of the frequency tb(i) in each power bandwidthPb(i)) of the vehicle with reference to the history of the vehicle powerPv acquired by the power acquiring unit 64 when the vehicle traveled theroute in the past.

The electric energy storage state acquiring unit 70 acquires a state ofcharge (SOC) in the rechargeable battery 16, that is, a remainingbattery capacity of the rechargeable battery 16, as the electric energystorage state of the electric energy storage device. Herein, the SOC(remaining battery capacity) of the rechargeable battery 16 can beestimated, for example, according to the current Ib and the voltage Vbof the rechargeable battery 16 detected by unillustrated sensors.

The operation condition setting unit 72 sets an engine operationcondition to control a charge-discharge balance of the rechargeablebattery 16 in a case where the vehicle travels the route from thedeparture point to the destination, that is, an energy balance betweengenerated power and generated electric power of the electric rotatingmachine (the motor 10 and the generator 54), to be at a preset value (orto fall within a preset range). Herein, the range of the requiredvehicle power Pv0 (the lower limit value Pc of the range) to operate theengine 50 is set as the engine operation condition using the powerfrequency distribution predicted by the power frequency distributionpredicting unit 68 (the value of the frequency tb(i) in each powerbandwidth Pb(i)) and the SOC (the remaining battery capacity) of therechargeable battery 16 acquired by the electric energy storage stateacquiring unit 70. A method of setting the range of the required vehiclepower Pv0 to operate the engine 50 (the engine operation condition) willbe described below in detail.

The operation control unit 60 then controls the operation of the engine50 according to the range of the required vehicle power Pv0 to operatethe engine 50 (the engine operation condition) set by the operationcondition setting unit 72. To be more concrete, when the requiredvehicle power Pv0 is larger than 0 and smaller than the lower limitvalue Pc of the range set by the operation condition setting unit 72,the operation control unit 60 stops the operation of the engine 50. Inshort, it controls the engine 50 so as to generate no power. In thisinstance, the operation control unit 60 generates power by means of themotor 10 and controls the EV (Electric Vehicle) travel by which thevehicle (the drive wheels 19) is driven by the power of the motor 10.Meanwhile, when the required vehicle power Pv0 falls within the rangeset by the operation condition setting unit 72 (equal to or larger thanthe lower limit value Pc of the range), the operation control unit 60controls the engine 50 to operate. In other words, it controls theengine 50 so as to generate power and drives the vehicle (the drivewheels 19) using the power of the engine 50. In this instance, it ispossible to convert some of the power (traveling power) of the engine 50to the generated electric power of the generator 54 so as to beaccumulated in the rechargeable battery 16. In addition, when therequired vehicle power Pv0 takes a negative value (while the vehicle isdecelerating by putting the brake on), the operation control unit 60controls the motor 10 to operate regeneratively, so that power(traveling power) of the drive wheels 19 (the vehicle) is converted tothe generated electric power of the motor 10 and accumulated in therechargeable battery 16.

An operation in a case where the vehicle travels from the departurepoint to the destination will now be described using the flowchart ofFIG. 5.

Initially, in Step S1, when the ignition is turned on by the driver tostart the vehicle, an ignition-on signal is read. Subsequently, in StepS2, the destination of the vehicle is inputted by the driver. The routeof the vehicle from the departure point to the destination is then setby the navigation system 36 and the route of the vehicle is predicted bythe route predicting unit 62. Subsequently, In Step S3, the powerfrequency distribution corresponding to the route of the vehiclepredicted in Step S2 is read out from the power frequency distributionstorage unit 66, so that the power frequency distribution in a casewhere the vehicle travels the route from the departure point to thedestination is predicted by the power frequency distribution predictingunit 68 with reference to the history of the vehicle power Pv when thevehicle traveled the route in the past. Then, the lower limit value Pcof the range of the required vehicle power Pv0 necessary to operate theengine (the engine operation condition) is set by the operationcondition setting unit 72 according to the power frequency distributionpredicted by the power frequency distribution predicting unit 68. In acase where there is no history of the vehicle power Pv when the vehicletraveled in the past in Step S3, the lower limit value Pc predeterminedas the reference is set by the operation condition setting unit 72.

In Step S4, the vehicle power Pv is acquired by the power acquiring unit64 while the vehicle is traveling from the departure point to thedestination, and the power frequency distribution stored (accumulated)in the power frequency distribution storage unit 66 is updated accordingto the vehicle power Pv thus acquired. To be more concrete, the vehiclepower Pv acquired by the power acquiring unit 64 is subjected tofiltering to remove noise. Then, in the power frequency distributioncorresponding to the route of the vehicle predicted by the routepredicting unit 62, the value of the frequency tb(i) corresponding tothe power bandwidth Pb(i) including the filtered vehicle power Pfv isupdated. The filtered vehicle power Pfv is expressed, for example, byEquation (1) below. In Equation (1) below, a is a time constant and z⁻¹is a time-lag operator.(Mathematical Formula 1)Pfv=(1−a/1−a·z ⁻¹)·Pv  (1)

In Step S5, whether the state of charge (SOC) of the rechargeablebattery 16 acquired by the electric energy storage state acquiring unit70 falls within the specified range (for example, a range of 50% to 70%both inclusive) is determined by the operation control unit 60 while thevehicle is traveling from the departure point to the destination. In acase where it is determined in Step S5 that the SOC of the rechargeablebattery 16 falls within the specified range, the operation control unit60 controls the operation of the engine 50 in Step S6 according to therange of the required vehicle power Pv0 to operate the engine 50 (underthe engine operation condition) set by the operation condition settingunit 72. In a case where it is determined that the required vehiclepower Pv0 is larger than 0 and smaller than the lower limit value Pc setby the operation condition setting unit 72, the operation control unit60 stops the operation of the engine 50 (controls the engine 50 togenerate no power), and executes the EV travel by which the vehicle isdriven by the power of the motor 10. In this instance, the operationcontrol unit 60 controls the operation of the motor 10 in such a mannerthat power generated by the motor 10 becomes equal to the requiredvehicle power Pv0. In a case where it is determined that the requiredvehicle power Pv0 is equal to or larger than the lower limit value Pc,the operation control unit 60 controls the engine 50 to operate(controls the engine 50 to generate power). In this instance, theoperation control unit 60 controls operations of the engine 50, themotor 10, and the generator 54 in such a manner that the rotationalspeed Ne and the torque Te of the engine 50 are positioned, for example,on the optimal fuel consumption line shown in FIG. 3 and the power ofthe vehicle (the drive wheels 19) becomes equal to the required vehiclepower Pv0.

Meanwhile, in a case where it is determined in Step S5 that the SOC ofthe rechargeable battery 16 is lower than the lower limit value of thespecified range (for example, 50%), the operation control unit 60controls the engine 50 to operate (controls the engine 50 to generatepower) in Step S6 independently of the range of the required vehiclepower Pv0 to operate the engine 50 (the engine operation condition) setby the operation condition setting unit 72. By controlling the generator54 to generate electric power using power of the engine 50 andcollecting the generated electric power of the generate 54 in therechargeable battery 16, the SOC of the rechargeable battery 16 isincreased. The rechargeable battery 16 is kept charged using the powerof the engine 50 until the SOC of the rechargeable battery 16 restoresto fall within the specified range (for example, 55% or higher). In acase where it is determined in Step S5 that the SOC of the rechargeablebatter 16 is higher than the upper limit value of the specified range(for example, 70%), the operation control unit 60 lowers the SOC of therechargeable battery 16 in Step S6 by controlling the motor to generatepower by supping electric power from the rechargeable battery 16 to themotor 10. The rechargeable battery 16 is kept discharged in this manneruntil the SOC of the rechargeable battery 16 drops to fall within thespecified range (for example, 65% or below).

Operations in Steps S4 through S6 as above are performed repetitively atpredetermined time intervals while the vehicle travels from thedeparture point to the destination (until the vehicle arrives at thedestination). After the arrival of the vehicle at the destination inStep S7 (the determination result is YES in Step S7), the ignition isturned off in Step S8.

Processing to set the range (the lower value Pc) of the required vehiclepower Pv0 to operate the engine 50 by the operation condition settingunit 72 in Step S3 will now be described in detail using the flowchartof FIG. 6.

Initially, in Step S101, the operation condition setting unit 72calculates a total power amount (a total power amount comparable toregeneration) Pbs to be accumulated in the rechargeable battery 16 bythe regenerative operation of the motor 10 in a case where the vehicletravels the route from the departure point to the destination using thepower frequency distribution (the power frequency distribution readoutfrom the power frequency distribution storage unit 66) predicted by thepower frequency distribution predicting unit 68. Herein, as is shown inFIG. 7, it is possible to calculate the total power amount Pbscomparable to regeneration using the negative power bandwidth Pb(i) andthe frequency tb(i) thereof in the power frequency distribution. To bemore concrete, the total power amount Pbs comparable to regeneration iscalculated in accordance with Equation (2) below. In Equation (2) below,η₁ is a conversion coefficient that takes into account the efficiencyuntil regenerative power is accumulated in the rechargeable battery 16.(Mathematical Formula 2)Pbs=η ₁(ΣPb(i)×tb(i))  (2)

Subsequently, in Step S102, the operation condition setting unit 72tentatively sets the lower limit value (hereinafter, referred to as thepower threshold value) Pc of the range of the required vehicle power Pv0to operate the engine 50 by choosing one threshold value candidate fromthreshold candidates provided in a plural form, [Pc(1), Pc(2), . . . ,and Pc(n)]. Subsequently, in Step S103, the operation condition settingunit 72 determines the range of the required vehicle power Pv0 toexecute the EV travel by which the vehicle is driven by the power of themotor 10 by stopping the operation of the engine 50 from the powerthreshold value Pc that has been chosen (set tentatively). Herein, arange larger than 0 and smaller than the power threshold value Pc is setas the range of the required vehicle power Pv0 to execute the EV travel.The operation condition setting unit 72 then calculates a total poweramount (a total power amount needed for the EV travel) Pevs to besupplied from the rechargeable battery 16 to the motor 10 in a casewhere the vehicle travels the route from the departure point to thedestination using the power frequency distribution. Herein, as is shownin FIG. 7, it is possible to calculate the total power amount Pevsneeded for the EV travel using the power bandwidth Pev(i) that is largerthan 0 and smaller than the power threshold value Pc and the frequencytev(i) thereof. To be more concrete, the total power amount Pevs of therechargeable battery 16 needed for the EV travel is calculated inaccordance with Equation (3) below. In Equation (3) below, η₂ is aconversion coefficient that takes into account the efficiency until thepower (electric power) of the rechargeable battery 16 is converted tothe power (traveling power) of the motor 10.(Mathematical Formula 3)Pevs=η ₂ ΣPev(i)×tev(i)  (3)

Subsequently, in Step S104, the operation condition setting unit 72 setsa total power balance amount between generated power and generatedelectric power of the motor 10 and the generator 54 in a case where thevehicle travels the route from the departure point to the destination,that is, a total power balance amount (a charge-discharge balanceamount) Pbts by charging and discharging the rechargeable battery 16.Herein, it is possible to set the total power balance amount Pbts of therechargeable battery 16 from a deviation of a target SOC of therechargeable battery 16 at the destination and the SOC (initial SOC) ofthe rechargeable battery 16 acquired by the electric energy storagestate acquiring unit 70 at the departure point of this journey. Also, itis possible to set the total power balance amount Pbts of therechargeable battery 16 from a deviation of the SOC of the rechargeablebattery 16 acquired at the destination and the SOC (initial SOC) of therechargeable battery 16 acquired at the departure point, in a case wherethe vehicle has traveled the route from the departure point to thedestination last time (in the past). It should be noted that the totalpower balance amount Pbts of the rechargeable battery 16 is positivewhen initial SOC<target SOC, and negative when initial SOC≧target SOC.

Subsequently, in Step S105, the operation condition setting unit 72calculates a total electricity generating power amount Pge of thegenerator 54 used to charge the rechargeable battery 16 in a case wherethe vehicle travels the route from the departure point to thedestination. Herein, the total electricity generating power amount Pgeof the generator 54 used to charge the rechargeable battery 16 iscalculated in accordance with Equation (4) below in order to achieve thetotal power balance amount Pbts set in Step S104. In Equation (4) below,η₃ is a conversion coefficient that takes into account the efficiencyuntil the power of the generator 54 is converted to the power of therechargeable battery 16.(Mathematical Formula 4)Pge=η ₃(Pevs+Pbs+Pbts)  (4)

Subsequently, in Step S106, the operation condition setting unit 72determines whether it is possible to set the operation conditions of theengine 50 and the generator 54 to achieve the total electricitygenerating power amount Pge under the condition of the power thresholdvalue Pc that is chosen (tentatively set). Herein, a range equal to orlarger than the power threshold value Pc is given as the range of therequired vehicle power Pv0 to operate the engine 50, and an electricitygenerating power Pch(i) of the generator 54 used to charge therechargeable battery 16 is set with respect to the power bandwidthPcup(i) (see FIG. 7) equal to or larger than the power threshold valuePc to operate the engine 50. In the description below, tcup(i) is givenas the frequency corresponding to the power bandwidth Pcup(i).

In a case where the rotational speed Ne and the torque Te of the engine50 are positioned on the optimal fuel consumption line described above,the characteristic of a fuel amount (fuel consumption rate) needed togenerate electric power of 1 kws with respect to the power (travelingpower) of the engine 50 is represented, for example, by a curve as isshown in FIG. 8. A region where electric power is generated by drivingthe engine 50 is determined according to the characteristic of FIG. 8.According to the characteristic shown in FIG. 8, for example, the fuelconsumption rate becomes the minimum when the power of the engine 50 isPc0 (Pc0>Pc). Accordingly, as is shown in FIG. 9, the electricitygenerating power Pch(i) that establishes Pcup(i)+Pchi(i)=(or ≦) Pc0 isset for each power bandwidth Pcup(i) that is larger than Pc and smallerthan Pc0. In other words, in each power bandwidth Pcup(i) that is largerthan Pc and smaller than Pc0, the power of the engine 50 is set to Pc0so as to minimize the fuel consumption rate of the engine 50. FIG. 9shows a case where the electricity generating powers Pch(1) and Pch(2)are set, respectively, for the power bandwidths Pcup(1) and Pcup(2) thatare larger than Pc and smaller than Pc0. When Equation (5) below isestablished, the total electricity generating power amount Pge can besupplied by the electricity generating powers Pch(1) and Pch(2) alone.(Mathematical Formula 5)Pge≦η ₃(Pch(1)×tcup(1)+Pch(2)×tcup(2))  (5)

In a case where Equation (5) above is established (in a case where thetotal electricity generating power amount Pge can be supplied by theelectricity generating powers Pch(1) and Pch(2) alone), thedetermination result in Step S106 is YES. In this case, it is possibleto set the power of the engine 50 and the generated electric power ofthe generator 54 in each power bandwidth Pcup(i) in such a manner thatthe SOC of the rechargeable battery 16 after the vehicle has traveledthe route from the departure point to the destination achieves thetarget SOC at the destination (the total power balance amount of therechargeable battery 16 becomes the total power balance amount Pbts setin Step S104) under the condition of the chosen power threshold valuePc. Then, the electricity generating power Pch(1) with respect to thepower bandwidth Pcup(1), for example, which is the lower powerbandwidth, is determined again so that the right side and the left sideof Equation (5) above become equal. The flow then proceeds to Step S107.In this instance, Pch(1) is expressed by Equation (6) as follows:(Mathematical Formula 6)Pch(1)=(Pge/η ₃ −Pch(2)×tcup(2))/tcup(1)  (6).

Meanwhile, in a case where Equation (5) above is not established (in acase where the total electricity generating power amount Pge cannot besupplied by the electricity generating powers Pch(1) and Pch(2) alone),the range of the power bandwidth Pcup(i) for which the generatedelectric power Pch(i) is set is broadened, and as is shown in FIG. 10,the electricity generating power Pch(i) is set again so thatPcup(i)+Pch(i)=(or Pc1 is established with respect to each powerbandwidth Pcup(i) that is larger than Pc and smaller than Pc1 (Pc1>Pc0).In other words, the power of the engine 50 is set again to Pc1 in eachpower bandwidth Pcup(i) that is larger than Pc and smaller than Pc1.FIG. 10 shows a case where the electricity generating powers Pch(1),Pch(2), and Pch(3) are set, respectively, with respect to the powerbandwidths Pcup(1), Pcup(2), and Pcup(3) that are larger than Pc andsmaller than Pc1. Subsequently, whether Equation (7) below isestablished (whether the total electricity generating power amount Pgecan be supplied by the electricity generating power Pch(1), Pch(2), andPch(3)) is determined.(Mathematical Formula 7)Pge≦η ₃(Pch(1)×tcup(1)+Pch(2)×tcup(2)+Pch(3)×tcup(3))  (7)

In a case where Equation (7) above is established, the determinationresult in Step S106 is also YES. In this case, too, it is possible toset the power of the engine 50 and the generated electric power of thegenerator 54 in each power bandwidth Pcup(i) in such a manner that theSOC of the rechargeable battery 16 after the vehicle has traveled theroute from the departure point to the destination achieves the targetSOC at the destination (the total power balance amount of therechargeable battery 16 becomes the total power balance amount Pbts setin Step S104) under the condition of the chosen power threshold valuePc. Then, the electricity generating power Pch(1) for the powerbandwidth Pcup(1) is determined again so that the right side and theleft side of Equation (7) above become equal. The flow then proceeds toStep S107.

Meanwhile, in a case where Equation (7) is not established, the range ofthe power bandwidth Pcup(i) for which the electricity generating powerPch(i) is set is broadened further to determine whether the totalelectricity generating power amount Pge can be supplied by theelectricity generating power Pch(i). It should be noted, however, thatit is determined that the total electricity generating power amount Pgecannot be supplied by the electricity generating power Pch(i) in a casewhere the total electricity generating power amount Pge cannot besupplied unless the power of the engine 50 in the power bandwidthPcup(i) exceeds the preset allowance value or in a case where the totalelectricity generating power amount Pge cannot be supplied unless theelectricity generating power Pch(i) of the generator 54 in the powerbandwidth Pcup(i) exceeds the preset allowance value. The result ofdetermination in Step S106 is therefore NO. In this case, it isdetermined that it is impossible to set the power of the engine 50 andthe generated electric power of the generator 54 in each power bandwidthPcup(i) in such a manner that the SOC of the rechargeable battery 16after the vehicle traveled the route from the departure point to thedestination reaches the target SOC (the total power balance amount ofthe rechargeable battery 16 becomes the total power balance amount Pbtsset in Step S104). The flow then proceeds to Step S108.

In Step S107, the operation condition setting unit 72 calculates a totalfuel consumption amount Fu of the engine 50 in a case where the vehicletravels the route from the destination to the destination using thepower bandwidth Pcup(i) equal to or larger than the power thresholdvalue Pc (the range of the required vehicle power Pv0 to operate theengine 50), the power of the engine 50 in the power bandwidth Pcup(i)set in Step S106, and the frequency tcup(i) (power frequencydistribution) in the power bandwidth Pcup(i). Herein, a total poweramount Ps(1) of the engine 50 in a case where the vehicle travels theroute from the departure point to the destination with respect to thepower threshold value Pc=Pc(1) is expressed by Equation (8) below. Thetotal fuel consumption amount Fu(1) of the engine 50 with respect to thepower threshold value Pc=Pc(1) is calculated using Equation (8) belowand the characteristic of the fuel consumption amount with respect tothe power of the engine 50 (see FIG. 11).(Mathematical Formula 8)Ps(1)=(Pcup(1)+Pch(1))×tcup(1)+(Pcup(2)+Pch(2))×tcup(2)+ . . .+Pch(m)×tcup(m)  (8)

Subsequently, in Step S108, the operation condition setting unit 72determines whether it has selected (tentatively set) the power thresholdvalue Pc with respect to all the threshold value candidates [Pc(1),Pc(2), . . . , Pc(n)]. In a case where the power threshold value Pc hasnot been chosen for all the threshold candidates (in a case where thedetermination result in Step S108 is NO), the flow returns to Step S102.Then, processing in Step S102 through S107 is repeated by changing thepower threshold value Pc (the range of the required vehicle power Pv0 tooperate the engine 50) to be chosen (tentatively set). Meanwhile, in acase where the power threshold value Pc has been chosen for all thethreshold candidates (in a case where the determination result in StepS108 is YES), the flow proceeds to Step S109.

In Step S109, the operation condition setting unit 72 determines thepower threshold value Pc (the lower limit value of the range of therequired vehicle power Pv0) chosen (tentatively set) in a case where thetotal fuel consumption amount is the minimum among all the total fuelconsumption amounts of the engine 50 calculated in Step S108 to be thelower limit value of the range of the required vehicle power Pv0 tooperate the engine 50. After the power threshold value Pc is determined,the operation control unit 60 controls the operations of the engine 50,the motor 10, and the generator 54 according to the power thresholdvalue Pc as described above. Herein, in a case where the requiredvehicle power Pv0 is included in the power bandwidth Pcup(i) equal to orlager than the power threshold value Pc, the engine 50 is operated andthe electricity generating power of the generator 54 used to charge therechargeable battery 16 is set to the electricity generating powerPch(i) that is set when the power threshold value Pc is determined. Inshort, the power of the engine 50 is controlled to be Pcup(i)+Pch(i).According to the processing described above, the power threshold valuePc (the engine operation condition) can be set for, in a case where thevehicle travels the route from the departure point to the destination,controlling the SOC of the rechargeable battery 16 to achieve the targetSOC at the destination (controlling the total power balance amount ofthe rechargeable battery 16 to become the total power balance amountPbts set in Step S104) and minimizing the total fuel consumption amountof the engine 50.

According to the processing described above, the charge-dischargebalance of the rechargeable battery 16 is calculated using the power(electric power) balance. However, the charge-discharge balance of therechargeable battery 16 may be calculated using a current balance. Forexample, a current of the rechargeable battery 16 is expressed by afunction f(P) of the power (electric power) P of the rechargeablebattery 16. Herein, f(P)≧0 when P≧0, and f(P)<0 when P<0.

In this case, a total current amount (a total current amount comparableto regeneration) Ibs to be charged to the rechargeable battery 16 by theregenerative operation of the motor 10 in a case where the vehicletravels the route from the departure point to the destination set inStep S101 is expressed by Equation (9) below using the function f(P). Inaddition, a total current amount (a total current amount needed for theEV travel) Ievs that is supplied to the motor 10 from the rechargeablebattery 16 in a case where the vehicle travels the route from thedeparture point to the destination set in Step S103 is expressed byEquation (10) below using the function f(P):(Mathematical Formula 9)Ibs=Σf(η₁ ·Pb(i))×tb(i)  (9)Ievs=Σf(η₂ ·Pev(i))×tev(i)  (10).

A total generated current amount Ige of the generator 54 used to chargethe rechargeable battery 16 in a case where the vehicle travels theroute from the departure point to the destination set in Step S105 isexpressed by Equation (11) as follows:Ige=Ievs+Ibs+Ibts  (11).

It should be noted that in Equation (11) above, Ibts is a total currentbalance amount of the rechargeable battery 16 in a case where thevehicle travels the route from the departure point to the destinationset in Step S104, and for example, it can be set from a deviation of thetarget SOC of the rechargeable battery 16 at the destination and the SOC(initial SOC) of the rechargeable batter 16 acquired at the departurepoint of this travel. Herein, Ibts is positive when initial SOC<targetSOC, and negative when initial SOC≧target SOC. In Step S106, whether itis possible to achieve the total generated current amount Ige with theelectricity generating power Pch(i) using the function f(P).

Also, in the processing described above, it is possible to set thetarget SOC of the rechargeable battery 16 at the destination to have arange to some extent in Step S104. The total power balance amount Pbtsof the rechargeable battery 16 can be also set to have a range to someextent.

In this embodiment as described above, the power threshold value Pc forcontrolling the charge-discharge balance of the rechargeable battery 16in a case where the vehicle travels the route, that is, the energybalance between the generated power and the generated electric power ofthe motor 10 and the generator 54, to be at the preset value (or to fallwithin the preset range) is set according to the power frequencydistribution of the vehicle over the entire route. The EV travel by themotor 10 is then executed when the required vehicle power Pv0 is largerthan 0 and smaller than the power threshold value Pc, and the engine 50is operated when the required vehicle power Pv0 is equal to or largerthan the power threshold value Pc. Hence, not only is it possible toallow the vehicle to travel using the power of the engine 50 under ahigh combustion efficiency condition, but it is also possible to allowthe vehicle to travel using the power of the motor 10 alone by stoppingthe operation of the engine 50 under a low combustion efficiencycondition while preventing the SOC (remaining battery capacity) of therechargeable battery 16 from increasing or decreasing exceedingly.Consequently, not only is it possible to control the SOC of therechargeable battery 16 when the vehicle arrives at the destination tobe at a desired value (or to fall within a desired range), but it isalso possible to enhance the fuel consumption of the engine 50. Hence,according to this embodiment, the operations of the engine 50, the motor10, and the generator 54 can be controlled more appropriately.

Further, in this embodiment, the power consumption of the engine 50 canbe further enhanced by setting the power threshold value Pc for, in acase where the vehicle travels the route, setting the energy balance tobe at the preset value (or to fall within the preset range) andminimizing the total fuel consumption amount Fu of the engine 50.

Also, in this embodiment, in a case where the SOC of the rechargeablebattery 16 drops below the specified range while the vehicle istraveling, it is possible to appropriately prevent the SOC of therechargeable battery 16 from reducing excessively by generating electricpower by means of the generator 54 by controlling the engine 50 togenerate power even when the required vehicle power Pv0 is smaller thanthe power threshold value Pc.

Also, in this embodiment, with respect to the power frequencydistribution used to set the power threshold value Pc, it is sufficientto store the frequency tb(i) in each of the power bandwidths Pb(i),which are the vehicle power Pv divided in advance. Hence, a data storageamount needed to set the power threshold value Pc can be reducedmarkedly. In addition, a variance of a travel resistance caused, forexample, by a slope, can be incorporated into the data as a powervariance by storing the frequency of the vehicle power (travelingpower). According, information about a road environment condition, suchas a road surface gradient, is unnecessary, which can also decrease thedata storage amount. Meanwhile, in Patent Document 1, the vehicle speedpattern is estimated zone by zone for the path divided into pluralzones. It is, however, difficult to detect the travel resistance, suchas slope information, from the vehicle speed pattern alone. In PatentDocument 1, the road environment information, various vehicle states,and an operation history of the driver are necessary to estimate thetravel resistance, which results in a significant increase of the datastorage amount.

Also, in Patent Document 1, whether the vehicle is to travel byoperating the motor or by operating the engine is set zone by zone forthe path divided into plural zones. Accordingly, in a case where aregion in which the required vehicle power is low and a region in whichthe required vehicle power is high are present together in the samezone, either the vehicle travels using a power of the engine even undera condition where the combustion efficiency of the engine is low, or thevehicle travels using a power of the motor even under a condition wherethe combustion efficiency of the engine is high. In contrast to thisconfiguration, in this embodiment, it is possible to set either that thevehicle is to travel by the EV travel using the power of the motor 10,or by the travel using the power of the engine 50, according to acomparison between the required vehicle power Pv0 and the powerthreshold value Pc. Hence, not only can the engine 50 be operated in areliable manner under a high combustion efficiency condition, but alsothe operation of the engine 50 can be stopped in a reliable manner undera low combustion efficiency condition.

Also, in Patent Document 1, the fuel consumption varies markedlydepending on in which zone the vehicle travels by operating the motorand in which zone the vehicle travels by operating the engine. In PatentDocument 1, it is disclosed to choose a zone in which the engine isoperated at an operation point at the lowest efficiency within theschedule zones immediately before the continued regenerative zone, asthe travel zone in which the vehicle travels by operating the motor.However, in order to enhance the fuel consumption for the entire route,besides the zone immediately before the continued regenerative zone, itis also necessary to determine where along the entire route the engineshould be operated and where along the entire route the vehicle shouldtravel by operating the motor using some conditions. In contrast to thisconfiguration, in this embodiment, by setting a range of the requiredvehicle power Pv0 to execute the EV travel by the motor 10 and the rangeof the required vehicle power Pv0 to operate the engine 50 according tothe power frequency distribution of the vehicle for the entire route,not only is it possible to operate the engine 50 only where thecombustion efficiency is high to the extent possible, but it is alsopossible to control the vehicle to travel by the motor 10 alone wherethe combustion efficiency is low while the vehicle is traveling theroute. Hence, fuel consumption for the entire route can be enhanced.

Another example of the configuration of this embodiment will now bedescribed.

In this embodiment, by dividing the route from the departure point tothe destination into plural travel zones for the power frequencydistribution storage unit 66 to store the power frequency distribution(the value of the frequency tb(i) in each power bandwidth Pb(i)) foreach travel zone, the power frequency distribution predicting unit 68becomes able to predict the power frequency distribution for each travelzone in a case where the vehicle travels the route from the departurepoint to the destination. Herein, the route from the departure point tothe destination can be divided into zones in reference to landmarks,such as intersections. The operation condition setting unit 72 maycorrect the range of the required vehicle power Pv0 to operate theengine 50 (the power threshold value Pc) each time the vehicle travelsin the respective travel zones. Hereinafter, an operation in a casewhere the power threshold value Pc is corrected will be described usingthe flowchart of FIG. 12.

Steps S11, S12, and S16 through S18 of the flowchart of FIG. 12 are thesame as Steps S1, S2, and S6 through S8 of the flowchart in FIG. 5,respectively. In Step S13, the power frequency distribution in a casewhere the vehicle travels the route from the departure point to thedestination is predicted by synthesizing the power frequencydistributions of the respective travel zones stored in the powerfrequency distribution storage unit 66. Subsequently, as in Step S3, therange of the required vehicle power Pv0 necessary to operate the engine50 (the power threshold value Pc) is set by the operation conditionsetting unit 72 according to the power frequency distribution thuspredicted.

In Step S14, the power frequency distribution stored in the powerfrequency distribution storage unit 66 is updated for each travel zonewhile the vehicle is traveling according to the vehicle power Pvacquired by the power acquiring unit 64. Herein, in the power frequencydistribution corresponding to a travel zone in which the vehicle istraveling, the value of the frequency tb(i) corresponding to the powerbandwidth Pb(i) including the vehicle power Pv (the filtered vehiclepower Pfv) is updated.

Also, in Step S15, the range of the required vehicle power Pv0 necessaryto operate the engine 50 (the engine operation condition) is correctedby the operation condition setting unit 72 each time the vehicle travelsthe respective travel zones. Hereinafter, the processing by theoperation condition setting unit 72 to correct the range of the requiredvehicle power Pv0 to operate the engine 50 (the power threshold valuePc) will be described in detail using the flowchart of FIG. 13.

Initially, in Step S201, the operation condition setting unit 72predicts the SOC of the rechargeable battery 16 after the vehicletraveled a travel zone R1 that the vehicle is to travel using a powerfrequency distribution P1 corresponding to the travel zone R1 and thepower threshold value Pc currently set.

Herein, a total current amount (a total current amount comparable toregeneration) Ileg to be charged to the rechargeable battery 16 by theregenerative operation of the motor 10 when the vehicle travels in thetravel zone R1 is expressed by Equation (12) below. Also, a totalcurrent amount (a total current amount needed for the EV travel) Ilevsto be supplied from the rechargeable battery 16 to the motor 10 when thevehicle travels in the travel zone R1 is expressed by Equation (13)below. In addition, a total generated current amount Ilegs of thegenerator 54 to be used to charge the rechargeable battery 16 in a casewhere the vehicle travels the travel zone R1 is expressed by Equation(14) below.(Mathematical Formula 10)I1eg=Σf(η₁ ·Pb(i))×tb(i)  (12)I1evs=Σf(η₂ ·Pev(i))×tev(i)  (13)I1egs=Σf(η₃ ·Pch(i))×tcup(i)  (14)

Also, a total current balance amount (the discharge side is negative andthe charging side is positive) ΔI of the rechargeable battery 16 in acase where the vehicle travels the travel zone R1 is expressed byEquation (15) as follows:ΔI=I1evs+I1eg+I1egs  (15).

Hence, the operation condition setting unit 72 becomes able to calculatea remaining battery capacity variance ΔSOC of the rechargeable battery16 in a case where the vehicle travels the travel zone R1 in accordancewith Equation (16) below. It then becomes possible to calculate aremaining battery capacity SOC1 of the rechargeable battery 16 after thevehicle has traveled the travel zone R1 from the ASOC and the currentremaining battery capacity of the rechargeable battery 16. In Equation(16) below, Kb is a coefficient used to convert the total current amountto the SOC variance amount according to the battery capacity.ΔSOC=ΔI/Kb  (16)

In view of the foregoing, it is possible to calculate the SOC1 inaccordance with Equation (17) below. In Equation (17) below, SOC0 is thecurrent SOC.SOC1=SOC0+ΔSOC  (17)

Subsequently, in Step S202, the operation condition setting unit 72determines whether the SOC1 thus calculated falls within the specifiedrange of S1 to S2 inclusive, that is, whether the charge-dischargebalance of the rechargeable battery 16 (a total power balance amountbetween generated power and generated electric power of the motor 10 andthe generator 54) in a case where the vehicle travels the travel zone R1falls within the preset range. In a case where SOC1>S2 in Step S202, thevalue of the power threshold value Pc is increased in Step S203 and theflow returns to Step S201. Then, a calculation is performed repetitivelyuntil the remaining battery capacity SOC1 of the rechargeable battery 16after the vehicle has traveled through the travel zone R1 establishesS1≦SOC1≦S2. Also, in a case where SOC<S1 in Step S202, the value of thepower threshold Pc is reduced in Step S204, and the flow returns to StepS201. Then, a calculation is performed repetitively until the remainingbattery capacity SOC1 of the rechargeable battery 16 after the vehiclehas traveled through the travel zone R1 establishes S1≦SOC1≦S2.Meanwhile, in a case where S1≦SOC1≦S2 is established in Step S202, theflow proceeds to Step S205 and the operation of the engine 50 iscontrolled according to the power threshold value Pc in a case whereS1≦SOC1≦S2 is established for the vehicle to travel in the travel zoneR1. According to the processing described above, in a case where it isdetermined that the SOC of the rechargeable battery 16 after the vehiclehas traveled through the travel zone R1 falls outside the specifiedrange (the total power balance amount of the rechargeable battery 16falls outside the preset range) with the power threshold value Pc (underthe engine operation condition) currently set, the power threshold valuePc is set again so that the SOC of the rechargeable battery 16 after thevehicle has traveled through the travel zone R1 falls within thespecified range (the total power balance amount of the rechargeablebattery 16 falls within the preset range).

While the vehicle is traveling in the travel zone R1, the powerfrequency distribution P2 in a case where the vehicle travels thefollowing travel zone R2 is predicted by synthesizing the powerfrequency distributions corresponding to the respective travel zonesfollowing the travel zone R1, which are stored in the power frequencydistribution storage unit 66. Then, as in Step S13, the power thresholdvalue Pc12 is set by the operation condition setting unit 72 accordingto the power frequency distribution P2 thus predicted. It should benoted, however, that when the power threshold value Pc12 is set whilethe vehicle is traveling the travel zone R1, the SOC1 is used as theinitial SOC. Further, after the vehicle has traveled through the travelzone R1, as in Step S13, the power threshold value Pc2 is set by theoperation condition setting unit 72 according to the power frequencydistribution P2. Herein, the SOC of the rechargeable battery 16immediately after the vehicle has traveled through the travel zone R1 isused as the initial SOC. In a case where the power threshold value Pc2has not been set before the vehicle starts to travel in the travel zoneR2, the operation of the engine 50 is controlled according to the powerthreshold value Pc12. In a case where the power threshold value Pc2 hasbeen set, the operation of the engine 50 is controlled according to thepower threshold value Pc2.

According to this example of the configuration, in a case where it isdetermined that the charge-discharge balance of the rechargeable battery16, that is, the energy balance between generated power and generatedelectric power of the motor 10 and the generator 54 in a case where thevehicle travels in the travel zone R1, falls outside the preset rangewith the power threshold value Pc currently set, the power thresholdvalue Pc is set again so that the charge-discharge balance (energybalance) of the rechargeable battery 16 falls within the preset range ina case where the vehicle travels the travel zone R1. Accordingly, itbecomes possible to set the power threshold value Pc correspondingly toa variance of the travel conditions of the vehicle. Hence, even when thetravel condition of the vehicle varies, not only can the SOC of therechargeable battery 16 when the vehicle arrives at the destinationachieve a desired value (or fall within a desired range), but also thefuel consumption of the engine 50 can be enhanced.

In the description above, the route predicting unit 62 predicts theroute in a case where the vehicle travels from the departure point tothe destination from the route set by the navigation system 36. However,according to this embodiment, the month, the day of the week, and thedeparture time when the vehicle traveled from the departure point to thedestination in the past may be stored in the electronic control unit 42in correlation with the departure point and the destination, so that theroute predicting unit 62 first predicts the destination by reading outthe destination corresponding to the month, the day of the week, and thedeparture time, and the departure point when the vehicle is to departfrom the departure point, and it then predicts the route from thedeparture point to the destination. Also, in this embodiment, a travelhistory (for example, the travel distance, a steering operation amount,etc.) when the vehicle traveled the route from the departure point tothe destination in the past may be stored in the electronic control unit42, so that a change of the destination can be predicted by comparingthe travel state of the vehicle while it is traveling (for example, atravel distance, a steering manipulation amount, etc.) with the travelhistory stored in the electronic control unit 42. In a case where achange of the destination is predicted, the power threshold value Pc isset again according to the power frequency distribution or thepre-determined reference power threshold value Pc is set again.

Also, in this embodiment, by configuring in such a manner that the powerfrequency distribution storage unit 66 stores the power frequencydistribution (the value of the frequency tb(i) in each power bandwidthPb(i)) at every preset time or every preset distance, the powerfrequency distribution predicting unit 68 becomes able to predict thepower frequency distribution in a case where the vehicle travels theroute at every preset time or every preset distance. In addition, inthis embodiment, the power frequency distribution storage unit 66 maystore the power frequency distributions by sorting them according to thedistribution profiles. For example, in a case where the power frequencydistribution storage unit 66 stores the power frequency distributions atevery preset time or every preset distance, power frequencydistributions of a similar profile can be stored collectively. Herein,it is possible to sort the power frequency distributions, for example,to a distribution in which the frequency tb(i) concentrates in a lowpower bandwidth Pb(i), a distribution in which the frequency tb(i)concentrates in a high power bandwidth Pb(i), and an intermediatedistribution between these two distributions.

Also, in this embodiment, the power acquiring unit 64 may acquire thevehicle power Pv together with the vehicle travel state, such as therotational speed Ne and the torque Te of the engine 50, the rotationalspeed Nm and the torque Tm of the motor 10, and the rotational speed Ngand the torque Tg of the generator 54 (or at least one of theforegoing). This configuration enables the power frequency distributionstorage unit 66 to store the vehicle travel state in correlation withthe power bandwidth Pb(i) in which the vehicle power Pv acquiredtogether therewith is included.

In this case, the operation condition setting unit 72 determines in StepS106 whether the rotational speed Ne of the engine 50 and the rotationalspeed Ng or the torque Tg of the generator 54 (or at least one of theforgoing) exceed the preset corresponding upper limit values (limitvalues) by the electricity generating power Pch(i) of the generator 54in each power bandwidth Pcup(i) when setting the electricity generatingpower Pch(i) of the generator 54 (and the power of the engine 50,Pcup(i)+Pch(i)) used to charge the rechargeable battery 16 with respectto each power bandwidth Pcup(i) (see FIG. 6) equal to or larger than thepower threshold value Pc. Herein, it is possible to predict therotational speed Ne of the engine 50 and the rotational speed Ng or thetorque Tg of the generator 54 in a case where the electricity generatingpower Pch(i) is set in the power bandwidth Pcup(i) according to thevehicle travel state stored in correlation with the power bandwidthPcup(i), that is, the rotational speed Ne and the torque Te of theengine 50 and the rotational speed Ng and the torque Tg of the generator54 (or at least one of the foregoing). In a case where the rotationalspeed Ne of the engine 50 and the rotational speed Ng or the torque Tgof the generator 54 (or at least one of the foregoing) that have beenpredicted are equal to or lower than the corresponding upper limitvalues in each power bandwidth Pcup(i), it is determined whether thetotal electricity generating power amount Pge can be supplied by a sumof the electricity generating powers Pch(i) that are currently set. Inother words, it is determined whether the SOC of the rechargeablebattery 16 after the vehicle has traveled the route from the departurepoint to the destination can achieve the target SOC at the destination(whether an energy balance between the generated power and the generatedelectric power of the motor 10 and the generator 54 in a case where thevehicle travels the route can be a total power balance amount Pbts)under the conditions of the power of the engine 50, Pcup(i)+Pch(i), andthe electricity generating power Pch(i) of the generator 54 currentlyset. Meanwhile, in a case where at least one of (or all of) therotational speed Ne of the engine 50 and the rotational speed Ng or thetorque Tg of the generator 54 that have been predicted exceeds thecorresponding upper limit in a given power bandwidth Pcup(i), theelectricity generating power Pch(i) in this power bandwidth Pcup(i) isreset to 0. Alternatively, the electricity generating power Pch(i) (andthe power of the engine 50, Pcup(i)+Pch(i)) is calculated againaccording to the vehicle travel state (the rotational speed Ne and thetorque Te of the engine 50, the rotational speed Ng and the torque Tg ofthe generation 54, etc.) stored in correlation with this power bandwidthPcup(i), so that the rotational speed Ne of the engine 50 and therotational speed Ng or the torque Tg of the generator 54 (or at leastone of the foregoing) are limited to the corresponding upper limitvalues or below in this power bandwidth Pcup(i). Then, it is determinedwhether the total electricity generating power amount Pge can besupplied by a sum of the electricity generating powers Pch(i) thuscalculated again.

According to this configuration, it is possible to set the powerthreshold value Pc in such a manner that the rotational speed Ne of theengine 50 and the rotational speed Ng or the torque Tg of the generator54 (or at least one of the foregoing) are limited to the correspondingupper limit values or below. It is thus possible to control the SOC ofthe rechargeable battery 16 when the vehicle arrives at the destinationto achieve a desired value (or to fall within a desired range) whilelimiting the rotational speed Ne of the engine 50 and the rotationalspeed Ng or the torque Tg of the generator 54 (or at least one of theforegoing).

Also, in this embodiment, the power acquiring unit 64 may acquire thevehicle power Pv together with a physical amount (vehicle travel state)relative to in-vehicle sounds, such as an in-vehicle sound pressure(detected, for example, by an unillustrated microphone). The powerfrequency distribution storage unit 66 may then store the vehicle travelstate relative to in-vehicle sounds in correlation with the powerbandwidth Pb(i) in which the vehicle power Pv acquired togethertherewith is included.

In this case, the operation condition setting unit 72 changes theelectricity generating power Pch(i) in Step S106 in response to thein-vehicle sound pressure by calculating the electricity generatingpower Pch(i) according to the in-vehicle sound pressure (the vehicletravel state relative to the in-vehicle sounds) stored in correlationwith the power bandwidth Pcup(i) when setting the electricity generatingpower Pch(i) of the generator 54 (and the power of the engine 50, Pcup(i)+Pch(i)) to be used to charge the rechargeable battery 16 withrespect to each power bandwidth Pcup(i) (see FIG. 6) equal to or largerthan the power threshold value Pc. For example, the electricitygenerating power Pch(i) (and the power of the engine 50, Pcup(i)+Pch(i))is increased (decreased) in response to an increase (decrease) of thein-vehicle sound pressure stored in correlation with the power bandwidthPcup(i). Alternatively, it is possible to calculate the electricitygenerating power Pch(i) (and the power of the engine 50, Pcup(i)+Pch(i))in such a manner that the in-vehicle sound pressure is limited to theupper limit value (limit value) or below in each power bandwidth Pcup(i)equal to or larger than the power threshold value Pc. Then, it isdetermined whether the total electricity generating power amount Pge canbe supplied by a sum of the electricity generating powers Pch(i) thathave been set. In other words, it is determined whether the SOC of therechargeable battery 16 after the vehicle has traveled the route fromthe departure point to the destination can achieve the target SOC (anenergy balance between generated power and generated electric power ofthe motor 10 and the generator 54 in a case where the vehicle travelsthe route can be a total power balance amount Pbts) under the conditionsof the power of the engine 50, Pcup(i)+Pch(i), and the electricitygenerating power Pch(i) of the generator 54 that are currently set.

According to this configuration, the operations of the engine 50 and thegenerator 54 are controlled in each power bandwidth Pcup(i) equal to orlarger than the power threshold value Pc in such manner that power ofthe engine 50 and generated electric power of the generator 54 areincreased by pre-determined amounts when in-vehicle sounds become louderor power of the engine 50 and generated electric power of the generator54 are decreased by pre-determined amounts when in-vehicle sounds becomelower, by increasing (decreasing) the electricity generating powerPch(i) in response to an increase (a decrease) of the in-vehicle soundpressure. It is thus possible to reduce the influence of noise generatedwhen the generator 54 generates electric power. Also, according to thisconfiguration, by setting the power threshold value Pc so that thein-vehicle sound pressure is limited to the upper limit value or below,it becomes possible to control the SOC of the rechargeable battery 16when the vehicle arrives at the destination to achieve a desired value(or to fall within a desired range) while limiting the in-vehicle soundpressure. It should be noted that as a physical amount relative to thein-vehicle sounds (vehicle travel state), the rotational speed Ne of theengine 50 (it is determined that the in-vehicle sound pressure increasesas the rotational speed increases), the vehicle speed V (it isdetermined that the in-vehicle sound pressure increases as the vehiclespeed increases), a suspension vibration acceleration (it is determinedthat the in-vehicle sound pressure increases as the vibrationacceleration increases), and so forth can be used in addition to thein-vehicle sound pressure.

The embodiments above described a case where the invention is applied toa hybrid vehicle of the configuration shown in FIG. 1. It should beappreciated, however, that the configuration of a hybrid vehicle towhich the invention is applicable is not limited to the configurationshown in FIG. 1, and for example, the invention is also applicable to aseries-type hybrid vehicle and a parallel-type hybrid vehicle.

While the embodiments of the invention have been described in detail, itshould be appreciated that the invention is not limited to theseembodiments, and can be implemented in various forms without deviatingfrom the scope of the invention.

The invention claimed is:
 1. A hybrid vehicle controller used in ahybrid vehicle capable of driving drive wheels using power generated byat least one of an engine and an electric rotating machine and capableof generating electric power of the electric rotating machine using thepower generated by the engine, the electric rotating machine beingcapable of sending electric power to and receiving electric power from,an electric energy storage device that stores electric energy, thehybrid vehicle controller comprising: an operation control unit thatcontrols operations of the engine and the electric rotating machineaccording to required vehicle power; a power frequency distributionpredicting unit that predicts a power frequency distribution of thevehicle in a case where the vehicle travels along a route, the powerfrequency distribution of the vehicle being expressed by a frequencyincluded in each of a plurality of power bandwidths into which a vehiclepower is divided in advance, each of the plurality of power bandwidthshaving a range of power; an electric energy storage state acquiring unitthat acquires an electric energy storage state of the electric energystorage device; and an operation condition setting unit that sets anengine operation condition for the electric energy storage state of theelectric energy storage device after the vehicle has traveled the routeso as to fall within a preset range according to the power frequencydistribution predicted by the power frequency distribution predictingunit and the electric energy storage state of the electric energystorage device acquired by the electric energy storage state acquiringunit, wherein: the operation condition unit controls an operation of theengine according to the engine operation condition set by the operationcondition setting unit; the power frequency distribution predicting unitpredicts the power frequency distribution of the vehicle in each travelzone for the route divided into plural travel zones; and in a case whereit is determined that the electric energy storage state of the electricenergy storage device falls outside the preset range after the vehiclehas traveled a given travel zone under the engine operation conditioncurrently set, the operation condition setting unit sets the engineoperation condition again for the electric energy storage state of theelectric energy storage device to fall within the preset range after thevehicle traveled the travel zone according to the power frequencydistribution in each travel zone predicted by the power frequencydistribution predicting unit.
 2. The hybrid vehicle controller accordingto claim 1, wherein: the operation condition setting unit sets theengine operation condition for the electric energy storage state of theelectric energy storage device after the vehicle has traveled the routeso as to fall within the preset range and for fuel consumption of theengine to be substantially minimum according to the power frequencydistribution predicted by the power frequency distribution predictingunit and the electric energy storage state of the electric energystorage device acquired by the electric energy storage state acquiringunit.
 3. The hybrid vehicle controller according to claim 1, wherein:the operation condition setting unit sets a range of the requiredvehicle power to operate the engine as the engine operation condition;and the operation control unit controls the engine to operate when therequired vehicle power falls within the range set by the operationcondition setting unit.
 4. The hybrid vehicle controller according toclaim 3, wherein: the operation condition setting unit is configured torepetitively perform tentative setting processing to tentatively set therange of the required vehicle power to operate the engine and todetermine whether it is possible to set engine power and generatedelectric power of the electric rotating machine in the range of therequired vehicle power so that the electric energy storage state of theelectric energy storage device after the vehicle has traveled the routefalls within the preset range under a condition of the tentatively setrange of the required vehicle power using the power frequencydistribution predicted by the power frequency distribution predictingunit while changing the range of the required vehicle power that is settentatively, and is configured to set the range of the required vehiclepower to operate the engine according to a determination result.
 5. Thehybrid vehicle controller according to claim 4, wherein: the operationcondition setting unit performs computation processing to compute a fuelconsumption amount of the engine in a case where the vehicle travels theroute using the engine power and the power frequency distributionpredicted by the power frequency distribution predicting unit in a casewhere it is determined that it is possible to set the engine power andthe generated electric power of the electric rotating machine in therange of the required vehicle power tentatively set, and sets the rangeof the required vehicle power tentatively set in a case where the fuelconsumption amount becomes minimum among fuel consumption amountscomputed in the computation processing as the range of the requiredvehicle power to operate the engine.
 6. The hybrid vehicle controlleraccording to claim 4, further comprising: a power acquiring unit thatacquires vehicle power in a case where the vehicle travels the routetogether with at least one of a torque or a rotational speed of theengine and the electric rotating machine; and a power frequencydistribution storage unit that stores the power frequency distributionof the vehicle with reference to a history of the vehicle power acquiredby the power acquiring unit, wherein: the power frequency distributionpredicting unit uses the power frequency distribution of the vehiclestored in the power frequency distribution storage unit as the powerfrequency distribution of the vehicle in a case where the vehicletravels the route; the power frequency distribution of the vehicle isexpressed by a frequency included in each of power bandwidths that arevehicle power divided in advance into plural bandwidths; the powerfrequency distribution storage unit stores at least one of the torque orthe rotational speed of the engine and the electric rotating machine incorrelation with the power bandwidth in which the vehicle power acquiredtogether therewith is included; and the operation condition setting unitis configured to compute the engine power and the generated electricpower of the electric rotating machine according to at least one of thetorque or the rotational speed of the engine and the electric rotatingmachine stored in correlation with each power bandwidth in such a mannerthat the rotational speed of the engine and the rotational speed or thetorque of the electric rotating machine become equal to or lower thancorresponding limit values in each power bandwidth included in the rangeof the required vehicle power tentatively set, and to determine whetherthe electric energy storage state of the electric energy storage deviceafter the vehicle traveled the route falls within the preset range undera condition of the engine power and the generated electric power of theelectric rotating machine that have been computed.
 7. The hybrid vehiclecontroller according to claim 4, further comprising: a power acquiringunit that acquires vehicle power in a case where the vehicle travels theroute together with a vehicle travel state; and a power frequencydistribution storage unit that stores the power frequency distributionof the vehicle with reference to a history of the vehicle power acquiredby the power acquiring unit, wherein: the power frequency distributionpredicting unit uses the power frequency distribution of the vehiclestored in the power frequency distribution storage unit as the powerfrequency distribution of the vehicle in a case where the vehicletravels the route; the power frequency distribution of the vehicle isexpressed by a frequency included in each of power bandwidths that arevehicle power divided in advance into plural bandwidths; the powerfrequency distribution storage unit stores the vehicle travel state incorrelation with a power bandwidth in which the vehicle power acquiredtogether therewith is included; and the operation condition setting unitis configured to compute the engine power and the generated electricpower of the electric rotating machine for the vehicle travel state tobe equal to or lower than a limit value in each power bandwidth includedin the range of the required vehicle power tentatively set, and todetermine whether the electric energy storage state of the electricenergy storage device after the vehicle has traveled the route fallswithin the preset range under a condition of the engine power and thegenerated electric power of the electric rotating machine that have beencomputed.
 8. The hybrid vehicle controller according to claim 1,wherein: the operation condition setting unit sets a lower limit valueof a range of the required vehicle power to operate the engine as theengine operation condition; and the operation control unit controls theengine to operate when the required vehicle power is equal to or largerthan the lower limit value of the range set by the operation conditionsetting unit, and stops the operation of the engine and controls anoperation of the electric rotating machine for the electric rotatingmachine to generate power when the required vehicle power is larger than0 and smaller than the lower limit value of the range set by theoperation condition setting unit.
 9. The hybrid vehicle controlleraccording to claim 1, wherein: the operation control unit controls theengine to operate regardless of the engine operation condition set bythe operation condition setting unit when the electric energy storagestate of the electric energy storage device acquired by the electricenergy storage state acquiring unit is lower than a specified value. 10.The hybrid vehicle controller according to claim 1, further comprising:a power acquiring unit that acquires vehicle power in a case where thevehicle travels the route, wherein the power frequency distributionpredicting unit predicts the power frequency distribution of the vehiclein a case where the vehicle travels the route with reference to ahistory of the vehicle power acquired by the power acquiring unit. 11.The hybrid vehicle controller according to claim 10, further comprising:a power frequency distribution storage unit that stores the powerfrequency distribution of the vehicle with reference to the history ofthe vehicle power acquired by the power acquiring unit, wherein thepower frequency distribution predicting unit uses the power frequencydistribution of the vehicle stored in the power frequency distributionstorage unit as the power frequency distribution of the vehicle in acase where the vehicle travels the route.
 12. The hybrid vehiclecontroller according to claim 1, further comprising: a route predictingunit that predicts the route of the vehicle, wherein the power frequencydistribution predicting unit predicts the power frequency distributionof the vehicle in a case where the vehicle travels the route accordingto the route of the vehicle predicted by the route predicting unit. 13.The hybrid vehicle controller according to claim 1, wherein: an electricmotor capable of driving the drive wheels and an electric generatorcapable of generating electric power using the power generated by theengine are provided as the electric rotating machine.